title: Identification of a pair of phospholipid:diacylglycerol acyltransferases from developing flax (Linum usitatissimum L.) seed catalyzing the selective production of trilinolenin.
abstract: The oil from flax (Linum usitatissimum L.) has high amounts of α-linolenic acid (ALA; 18:3(cis)(Δ9,12,15)) and is one of the richest sources of omega-3 polyunsaturated fatty acids (ω-3-PUFAs). To produce ∼57% ALA in triacylglycerol (TAG), it is likely that flax contains enzymes that can efficiently transfer ALA to TAG. To test this hypothesis, we conducted a systematic characterization of TAG-synthesizing enzymes from flax. We identified several genes encoding acyl-CoA:diacylglycerol acyltransferases (DGATs) and phospholipid:diacylglycerol acyltransferases (PDATs) from the flax genome database. Due to recent genome duplication, duplicated gene pairs have been identified for all genes except DGAT2-2. Analysis of gene expression indicated that two DGAT1, two DGAT2, and four PDAT genes were preferentially expressed in flax embryos. Yeast functional analysis showed that DGAT1, DGAT2, and two PDAT enzymes restored TAG synthesis when produced recombinantly in yeast H1246 strain. The activity of particular PDAT enzymes (LuPDAT1 and LuPDAT2) was stimulated by the presence of ALA. Further seed-specific expression of flax genes in Arabidopsis thaliana indicated that DGAT1, PDAT1, and PDAT2 had significant effects on seed oil phenotype. Overall, this study indicated the existence of unique PDAT enzymes from flax that are able to preferentially catalyze the synthesis of TAG containing ALA acyl moieties. The identified LuPDATs may have practical applications for increasing the accumulation of ALA and other polyunsaturated fatty acids in oilseeds for food and industrial applications.
authors.affiliation: Department of Agricultural, Food, and Nutritional Science, Agricultural Lipid Biotechnology Program, University of Alberta, Edmonton, Alberta T6G 2P5, Canada.
authors.forename: Xue
authors.initials: X
authors.lastname: Pan
authors.forename: Rodrigo M P
authors.initials: RM
authors.lastname: Siloto
authors.forename: Aruna D
authors.initials: AD
authors.lastname: Wickramarathna
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Mietkiewska
authors.forename: Randall J
authors.initials: RJ
authors.lastname: Weselake
mesh_terms: D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics; D055162:Biocatalysis / Q000187:drug effects; D051048:Diacylglycerol O-Acyltransferase / Q000378:metabolism; D004952:Esters / Q000378:metabolism; D019597:Flax / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D008401:Gas Chromatography-Mass Spectrometry; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D005816:Genetic Complementation Test; D009154:Mutation / Q000235:genetics; D009928:Organ Specificity / Q000187:drug effects / Q000235:genetics; D010641:Phenotype; D010938:Plant Oils / Q000378:metabolism; D030821:Plants, Genetically Modified; D060888:Real-Time Polymerase Chain Reaction; D011995:Recombination, Genetic / Q000187:drug effects / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D012639:Seeds / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D013379:Substrate Specificity / Q000187:drug effects; D014280:Triglycerides / Q000096:biosynthesis*; D017962:alpha-Linolenic Acid / Q000494:pharmacology
chemical_list: D004952:Esters; D010938:Plant Oils; D014280:Triglycerides; D017962:alpha-Linolenic Acid; D000217:Acyltransferases; C426836:phospholipid diacylglycerol acyltransferase; D051048:Diacylglycerol O-Acyltransferase; C101314:trilinolenin
keywords: Flax; Lipid Metabolism; Metabolic Engineering; Molecular Genetics; Phospholipid:diacylglycerol Acyltransferases; Plant Molecular Biology; Triacylglycerol; α-Linolenic Acid